TUNNEL boring machines Florence and Cecilia have passed the halfway point in their excavation of the 10-mile, twin bore tunnel that will take HS2 under the Chiltern hills between West Hyde and South Heath in Buckinghamshire.
Since being launched in May and June 2021 respectively, the 2000 tonne, 170-metre (558 feet) long TBMs have removed more than 1.3 million cubic metres of chalk and flint during the course of their underground journeys. This quantity of material would be sufficient to fill more than 500 Olympic swimming pools, and it will be used to create chalk grassland at the tunnel’s southern portal as part of 127 hectares (314 acres) of new landscaping and wildlife habitats.
In addition to the boring and lining work, engineers have completed the excavation of the five shafts that will provide ventilation for emergency access to the tunnel. At the nearest to the southern portal (close to Chalfont St Peter), the first breakthrough from the tunnel’s cross passageway to the shaft has also been finished. The other shafts are located at Chalfont St Giles, Amersham, Little Missenden and Chesham Road. “The whole team has put in a fantastic effort over the last year-and-a-half and I’d like to congratulate the crews of both Florence and Cecilia for passing this important tunnelling milestone, and thank them for all their hard work,” commented HS2 Ltd’s head of tunnel engineering Martyn Noak.
A lined section of the tunnel with some of the equipment being used to complete its construction.
HS2